<template>
    <span class="s-canvas"
          @click="changeCode">
      <canvas id="s-canvas"
              ref="identifyCode"
              :width="contentWidth"
              :height="contentHeight"></canvas>
    </span>
  </template>
  
  <script>
import store from "@/store";

  export default {
    data () {
      return {
        identifyCode: ""
      }
    },
    props: {
      identifyCodes: {
        //验证码从该字段中抽取生成
        type: String,
        default: "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
      },
      fontSizeMin: {
        // 字体最小值
        type: Number,
        default: 25
      },
      fontSizeMax: {
        // 字体最大值
        type: Number,
        default: 35
      },
      backgroundColorMin: {
        // 验证码图片背景色最小值
        type: Number,
        default: 200
      },
      backgroundColorMax: {
        // 验证码图片背景色最大值
        type: Number,
        default: 220
      },
      dotColorMin: {
        // 背景干扰点最小值
        type: Number,
        default: 60
      },
      dotColorMax: {
        // 背景干扰点最大值
        type: Number,
        default: 120
      },
      contentWidth: {
        //容器宽度
        type: Number,
        default: 100
      },
      contentHeight: {
        //容器高度
        type: Number,
        default: 44
      }
    },
    watch: {
      identifyCode () {
        this.drawPic();
      }
    },
    mounted () {
      this.drawPic();
      this.makeCode(this.identifyCodes, 4);
    },
    methods: {
      // 生成一个随机数
      randomNum (min, max) {
        return Math.floor(Math.random() * (max - min) + min);
      },
      // 生成一个随机的颜色
      randomColor (min, max) {
        let r = this.randomNum(min, max);
        let g = this.randomNum(min, max);
        let b = this.randomNum(min, max);
        return "rgb(" + r + "," + g + "," + b + ")";
      },
      drawPic () {
        let canvas = document.getElementById("s-canvas");
        let ctx = canvas.getContext("2d");
        ctx.textBaseline = "bottom";
        // 绘制背景
        ctx.fillStyle = this.randomColor(
          this.backgroundColorMin,
          this.backgroundColorMax
        );
        ctx.fillRect(0, 0, this.contentWidth, this.contentHeight);
        // 绘制文字
        for (let i = 0; i < this.identifyCode.length; i++) {
          this.drawText(ctx, this.identifyCode[i], i);
        }
        this.drawLine(ctx);
        this.drawDot(ctx);
      },
      drawText (ctx, txt, i) {
        ctx.fillStyle = this.randomColor(50, 160); //随机生成字体颜色
        ctx.font =
          this.randomNum(this.fontSizeMin, this.fontSizeMax) + "px SimHei"; //随机生成字体大小
        let x = (i + 1) * ((this.contentWidth - 10) / (this.identifyCode.length + 1));
        let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5);
        var deg = this.randomNum(-30, 30);
        // 修改坐标原点和旋转角度
        ctx.translate(x, y);
        ctx.rotate((deg * Math.PI) / 180);
        ctx.fillText(txt, 0, 0);
        // 恢复坐标原点和旋转角度
        ctx.rotate((-deg * Math.PI) / 180);
        ctx.translate(-x, -y);
      },
      drawLine (ctx) {
        // 绘制干扰线
        for (let i = 0; i < 4; i++) {
          ctx.strokeStyle = this.randomColor(100, 200);
          ctx.beginPath();
          ctx.moveTo(
            this.randomNum(0, this.contentWidth),
            this.randomNum(0, this.contentHeight)
          );
          ctx.lineTo(
            this.randomNum(0, this.contentWidth),
            this.randomNum(0, this.contentHeight)
          );
          ctx.stroke();
        }
      },
      drawDot (ctx) {
        // 绘制干扰点
        for (let i = 0; i < 30; i++) {
          ctx.fillStyle = this.randomColor(0, 255);
          ctx.beginPath();
          ctx.arc(
            this.randomNum(0, this.contentWidth),
            this.randomNum(0, this.contentHeight),
            1,
            0,
            2 * Math.PI
          );
          ctx.fill();
        }
      },
      /*切换验证码start*/
      changeCode () {
        this.identifyCode = "";
        this.makeCode(this.identifyCodes, 4);
      },
      makeCode (e, n) {
        for (let i = 0; i < n; i++) {
          this.identifyCode += e[this.randomNum(0, e.length)];
        }
        store.commit("setVerifyCode", this.identifyCode)
        this.$emit("update:changeCode", this.identifyCode);
      }
    }
  };
  </script>
  
  